A person with Parkinson's disease who is receiving levodopa may experience "off" and "on" periods during the day.
Early in the course of the disease a patient treated with levodopa will show good clinical benefit without motor problems. Over time the patient may experience intervals of relatively normal functioning alternating with intervals of motor dysfunction.
Phenomenon
Correlated with
Clinical Findings
"on"
high levodopa levels
dyskinesias (turned on)
"off"
low levodopa levels
bradykinesias (turned off)
Dyskinesias may include choreiform movements affecting various muscle groups.
"Wearing off" refers to the effects seen at the end of a dosage cycle when the plasma levels of levodopa are at their lowest levels.
More frequent administration or continuous infusion is one way to minimize the highs and lows of drug levels in the plasma. As the disease progresses the loss of dopaminergic cells in the nigrostriatal system may contribute to an altered response to levodopa.
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